Alternator variants ?

[ratman]

Whilst assessing the jobs I need to do to tidy up the engine bay on my S3 I had a look at the alternator. It is a Bosch one rated at 55A but having looked at the alternate parts lists the ones quoted are both 65A. To further complicate matters I trawled the forums where somebody suggested using a 90A rated one. What is the norm for an S3 (TVR rules accepted !) and what are the implications of running a lower or higher rated one? Thanks guys.

[pies]

Lower power one run will eventually mean you draw power from the battery
Cant see an obvious problem with a higher rated one but no doubt someone will no if there is

[ratman]

Thanks as always Colin. Regards other topic (micro switch) will get photos tomorrow hopefully.

[nzdave]

It is not only TVR that has more than one standard. My Sierra V6 manual (used for reference when working on my S1) lists 14 different alternators from 4 different manugfactireres. Interesting there is no 65 amp alternator listed.
You need a bigger alternator if you run more electrical equipment especially things like driving lights and higher rated headlights.
Too small an alternator will result in slow or no charging of the battery when you use all the electrics (or at least all that work!). A larger alternator should not overcharge the battery as all have regulators to prevent this happening, but if you don't need it the standard one should be okay.